1. Field of the Invention
The present invention relates to connection links for chains and, in particular, to connection links for tram chains used in the mining industry.
2. Description of the Invention Background
In the materials mining industry, especially in the underground mining of coal and the like, conveyors are used to transport the mined ore from the seam. Such conveyors are generally chain driven or utilize chain to drive various pieces of machinery or haulage vehicles. One type of conveyor that specifically uses chain in its operation is known as a mobile articulated conveyor. Such conveyor provides for continuous transport of the discharge of a continuous mining machine to a main conveyor as the mining machine advances into the mine faze and changes the direction of its forward movement. The articulated conveyor includes a plurality of pivotally connected framework elements. The framework elements cooperate to support a driveable conveyor belt. The articulated conveyor system is moved along the mine surface by separate traction drive means which generally consists of a driven endless crawler or tram chain that has a series of crawler pads attached to the chain links. In order to facilitate installation, removal and repair of such endless tram chain, the chain is assembled with connection links that permit the chain to be separated.
A prior connection link design is illustrated in FIGS. 1, 2 and 3. As shown in FIG. 3, the prior design 200 generally consists of a "U"-shaped member 212 that has a central bottom member 214 from which extends a first leg 216 and a second leg 218. First leg 216 and second leg 218 are connected to the ends of central bottom member 214 such that they extend generally perpendicularly therefrom. However, as shown in FIG. 3, first leg 216 and second leg 218 extend inward toward one another. Both first leg 216 and second leg 218 include an enlarged heel portion shown as 220a and 220b, respectively. Enlarged heel portions 220a and 220b are provided to extend toward one another so that the distance between first leg 216 and second leg 218, which forms an opening 222, is substantially narrower than the primary opening 224 formed between the legs 216 and 218. Accordingly, there is provided a central opening 223 which is bounded by first opening 222, elongated heels 220 and central bottom member 214.
In accordance with the connection process, a first tram chain link 226, generally oval in shape in plan view and of circular cross-section which has an elongated opening therethrough, is entered through first opening 222 and hooked over first leg 216. A similar second tram chain link 228 is entered through first opening 222 and is hooked over second leg 218. The first chain link 226 and second chain link 228 are separated in central opening 223 by separating member 215 on bottom member 214. Separating member 215 is centrally disposed within primary opening 224 and is connected to central bottom member 214 such that it extends generally perpendicularly therefrom. Finally, first chain link 226 and second chain link 228 are retained in position by a crawler pad assembly, generally shown as 230, which is adapted for releasable connection to "U"-shaped member 212. As shown in FIGS. 1 and 2 crawler pad assembly 230 includes two (2) oppositely extending lateral crawler pad members 232 and 234. Crawler pad members 232 and 234 are releasably connected to "U"-shaped member 212 by cap screws 231 that extend through apertures 221a and 221b located in enlarged heel portions 220a and 220b, respectively, of "U"-shaped member 212. Cap screws 231 are then threadably received in corresponding threaded apertures 236 and 238 located in crawler pad members 232 and 234, respectively. First chain link 226 and second chain link 228 are retained in a relatively static position within central opening 223 by lock block 240 which is a separate element of crawler pad assembly 230 which is retained between crawler pad members 232 and 234.
As can be seen from FIGS. 1, 2 and 3, the prior design has disadvantages in several respects. In particular, the narrow nature of first opening 222 requires that a sufficient amount of chain slack be present in order to permit first chain link 226 and second chain link 228 to be hooked over enlarged heel portions 220. Oftentimes, in order to achieve the necessary slack, the tram chain drive sprockets must be moved or, in the alternative, the tram chain must be removed from the drive sprockets. Moreover, as the crawler pads advance and grip the mine surface, they tend to become partially embedded in the mine floor which thereby increases the difficulty in achieving even small amounts of chain slack.
Another serious problem inherent in the prior design is the failure of the cap screws that retain the crawler pads to the "U"-shaped members. As shown in FIG. 1, crawler pad assembly 230 is transversely mounted with respect to the axis of chain travel. Cap screws 231 are also mounted in a direction that is traverse to the axis of chain travel. Accordingly, it is not uncommon for the crawler pads to twist about the axis of travel as they encounter the irregularities of the mine floor. Such twisting action causes shear forces to develop at cap screws 231 which result in metal fatigue and over time ultimately cause cap screw failure.
The subject invention is directed toward an improved design for connection links for tram chains which overcomes, among others, the above-discussed problems and which provides for a more useful means of tram chain connection which does not require as much chain slack to be present during the connection process. In addition, the new connection link design eliminates connector failure caused by shear forces developed during the conveying process.